1. Field of the Invention
The present invention relates to the application of so-called dust jackets to books and particularly to the pre-treatment of unfolded protective paper jackets in the interest of insuring the proper fitting thereof to book covers. More specifically, this invention is directed to apparatus which facilitates the mechanized application of a paper jacket to a book cover and especially to apparatus for performing a conditioning apparatus on an unfolded jacket prior to folding the projecting side portions thereof around the longitudinal edges of an opened cover of a book. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
Methods and apparatus for the application of dust jackets to books are well known in the art. Thus, by way of example, published German application P 11 03 294 discloses an apparatus in which books, with the spines facing downwardly, are positioned upon unfolded jackets. The book covers are then opened outwardly from the book block at an angle which will be in the range between 55 and 57.5 degrees. The projecting side edge portions of the jackets are thereafter folded around the longitudinal edges of the opened cover to form flaps and the books are reclosed thus capturing the jackets in the desired position where they are wrapped around the books. Tight wrapping of the jackets around the books is, of course, desired. However, tight wrapping is resisted by the stiffness of the jacket material and, accordingly, jacket application methods and apparatus of the type shown in the referenced German application do not provide satisfactory results. Restated, as a consequence of the recovery force exerted by the jacket material, it is frequently impossible to avoid having the covers of the book reopen and slip out of the flaps which are formed in the jacket during folding thereof. Any such separation of the book cover from the jacket flap must be corrected by hand and such correction is a labor intensive and thus expensive operation. It is to be noted that the liklihood of a book cover reopening after jacket application increases if the jacket material is relatively thick or if the jacket material has a coating.
The book making industry has long sought a satisfactory method of applying jackets to book covers, i.e., a method which will ensure a high quality product. Poorly fitting jackets result in books having an unsightly appearance. Additionally, poorly fitting jackets significantly interfere with subsequent processing operations such as, for example, individual packaging of the jacketed books in a shrink film. Further, and most importantly, poorly fitting jackets have a tendency to interfere with the handling of a book by the end user.
To further discuss prior art efforts to apply jackets to book covers, it has long been known that the distance between the oppositely disposed front edges of a book cover, measured around the book spine, is greater when the book is closed than when the book covers have been opened outwardly. Accordingly, the folding of a jacket around the edges of a book cover which is held at a relatively large opening angle necessarily leads to excessively tight fitting of the jacket. A excessively tight fit of the jacket increases the liklihood of cover reopening and separation of the book cover from the jacket fold.
It is to be noted that, in an effort to avoid the above-discussed problems associated with the reopening of the book covers as a consequence of the recovery forces exerted by jacket materials, the above-referenced German application suggests that the jacket be creased or scored prior to folding around the cover. Such creasing or scoring will reduce the recovery forces exerted by the inwardly folded material. However, creasing or scoring does not exclude the possibility that the creases will slip over the edge of the cover or that the jacket will not be wrapped sufficiently tightly around the book. Such slippage or a failure to achieve tight wrapping are inherent possibilities due to the existence of unavoidable manufacturing tolerances. Restated, it is not always possible for there to be dimensional coincidence between the inter-crease length and the setting of the creasing elements. Further, and this is particularly true in the case of coated jackets, the step of forming creases invariably results in the surface of the jacket cracking and such cracks result in an unsightly, and thus unacceptable, appearance.
Another example of a prior art technique for wrapping protective jackets around books may be seen from German Patent 26 20 047. The technique of this German patent involves wrapping an unfolded jacket around a book cover that has been swung outwardly, i.e., away from the book block. The wrapped cover is then folded around the opposite longitudinal edges of the book cover to form the retention flaps and the book is thereafter reclosed. In the technique of this German patent, the book covers are swung away from the book block, i.e., are opened to an angle of approximately 30.degree., and heat is applied during the folding operation. While the desired tight fitting of the jackets can be achieved by the application of heat during the folding operation, the technique of German Patent 26 20 047 does not eliminate the above-discussed problem of separation of the book cover from the jacket fold.